Glow plug



June' 18, 1940. A F, KUNGNER 2,205,145

lsnow `PLUG Filed hay 23, 1939 ATTORNEY no start.

Patented June 18, 1940 UNITED STATES RTENT OFFICE GLOW PLUG ApplicationMay 23, 1939, Serial No. 275,171

10 Claims.

This invention relates to a glow plug especially adapted for use in thecylinder of an internal combustion engine,v and particularly in thecylinder of a Diesel engine. Such engines are hard to start and in orderto assist the compression in generating sufficient heat to ignite themixture, glow plugs have been used.

In such a plug, a resistance wire heating element is mounted at the endso that when electric current is passed through it from a suitablesource, frequently a storage battery, the heating element is raised intemperature, preferably to red heat or hotter.y The heating element isdisposed in the most practical location and this local auxiliary heatwhich is thus generated by the heating element within the engine greatlyaids in starting it.

In my many years of experience in building spark plugs for internalcombustion engines and 2 also in building glow plugs, I have encounteredmany difficulties in constructing the latter type of plug. One of thegreat diliculties which'I have encountered is that of mounting theresistance unit so that it will not become loose in the electrodeelements which support it. The end oi the plug carrying the glow unit issubjected to high temperature and pressures and the deterioratinginfluences of the fuel, all of which tend to loosen all the joints andincrease the resistance at the union of the glow unit and its supportmembers, so that the current from the electrical source is cut down tosuch a point as to seriously affect or actually eliminate the action ofthe plug. In other words, the heating is impaired or lost altogether sothat the whole purpose of the plug is defeated.

There is another harmful aspect of insecure electrical joints in glowplugs. In multi-cylinder engines, the several glow plugs may be, andusually are, connected in series with each other. Thus an unreliableelectrical joint in any one plug will increase the resistance of thecircuit as whole and diminish the heating current to all plugs. In sucha case the desired and calculated v l4;, amount of heat would not beavailable at any cylinder even though several of the glow plugs be not,at that time, impaired.

Furthermore, whatever the number of cylinn ders and number of glowplugs, uniformity oi .no behavior is essential and such uniformity isnot attainable if the integrity of the electrical joints cannot berelied. upon. For example, an engine user learns the approximate lengthof time to apply current to yield heat to give an easy Ii the glow plugresistance be increased (Cl. 12S- 145) by reason of an imperfectelectrical joint, the expected result will not Occur. Repeated secondaryapplications of heat may be needed. The user may be entirely unaware ofthe nature of the difficulty and be put to great annoyance and 5 even tosubstantial expense occasioned by thev obscure nature of the fault asmuch as by the existence of the fault itself.

It is therefore the principal object of my invention to provide a glowplug which will overl0 come the objections which I have encounteredini--I past experience in the lconstruction of such devices, certain ofthese objections being as above stated.

The construction of my improved type of 'glow lo plug will be readilyunderstood by reference toA the annexed drawing, wherein:

Figure l is a full-size view of an element, partly in elevation andpartly in section, of a two-pole type of glow plug unit per se, withoutthe shell 2U used for mounting it in the engine.

Figure 2 is a View of Figure l turned ninety degrees.

Figure 3 is a View of the glow unit ready to be assembled to theelectrodes supporting it. 25

Figure Il is a view of the sleeve mounting element shown in. Figures 1and 3.

Figure 5 is a View oi the glow end of a singlepole unit.

Figure 6 is a View similar to Figure 5, but 30 showing the use of two ofthe sleeves of Figure 4.

In the drawing, Figure 1 shows a plug element generally referred to asof the series or two-pole type, in which a number of similar plugs indifferent cylinders may be connected in series with a source of current.In this construction,

l is a shell by means of which the plug element may be attached to amounting member going to the engine cylinder. Within the shell l thereis mounted a member 2 which is hollow at one 40 end, having a stem 3which is threaded to receive a nut 4.

The member 2 is insulated from the member l by suitable insulatingmaterial 5, such as mica. Within the member 2 is a central electrode 6which extends through the stem 3 but is insulated therefrom andterminates in the threaded end 'l carrying a nut Between the nuts 4 andi there is mounted an insulator 9 having metal collars Iii and il. Themetal collar Il contacts 50 with a metal bushing 24 on the threadedend 1. The bushing 24 is insulated from the electrode 2 by an insulator25. By this arrangement one terminal wire may be connected between thenut 4 and the metallic collar l0, while the other is 55 connectedbetween the nut 8 and metallic collar II, thereby completing electricalconnections to the electrodes 2 and 6. The end I2 of the electrode 2 isinsulated from the end I3 of the electrode 5 by a satisfactory insulatorIII such as mica.

For at least a part of the distance between the ends I2 and I3, and theends carrying the terminal contacts, as just described, an air space I5may be provided.

The glow unit as shown in Figure 3, comprises a wire of resistancematerial bent into the desired form, such as a loop I6. One arm I'I ofthe unit is passed through a sleeve I8, the end of which is beveled atI9 so that when the sleeve I8 is in the position shown in Figure 3, theend 'i of the wire is welded or brazed thereto, forming a fusion jointat the point 20. With the unit assembled as in Figure 3, the sleeve I 8,which has a slight taper, being of smaller diameter at the end I9, isforced into a cooperative, slightly tapered hole 2l in the end of theelectrode 5, while the other arm 22 of the glow member is forced into ahole in the electrode I2, after which it is spot-welded into position at23.

From the foregoing description, it will be seen that the sleeve I8 maybe assembled as described to the glow member and when the unit isassembled as shown in Figure 1, the fusion joint 20 is a considerabledistance within the relatively massive end I3 of the electrode 6 so thatthe joint is protected from the direct action of gases and pressureswithin the engine cylinder. The sleeve I8 is preferably made of amaterial whereby it will have a coeicient of expansion substantially thesame as its supporting electrode, so that the danger of loosenessoccurring at their junction point is reduced to a minimum. By way ofexample, but not of limitation, I have used stainless steel for both thesleeve I8 and the electrode 6, referring to Figure l. It is obvious thatonly the inner or glow end of the electrode 6 need be made of a materiallike that of the sleeve I8. I prefer to make the glow wire from an alloyof chrome and aluminum as nickel is more susceptible to attack by theelements of combustion.

In the devices shown in Figures l and 5, the space for which theseparticular plugs were made is not sufficient to allow the use of asleeve I8 on the arm 22, hence the spot-welding operation 23. I havefound that most of the trouble with glow plugs has been in the unionbetween the glow wire and the central electrode, but where spacepermits, the arm 22 may also be provided with a sleeve I8 as is shown inFigure 6.

The construction herein described is much cheaper than any otherconstruction of which I am aware, and from the tests that I have made, Ihave found it to be more satisfactory than any other glow plug which Ihave ever constructed or of which I have knowledge.

What I claim is:

1. A glow plug including; a central electrode,

n a cooperative adjacent electrode insulated from the central electrode,and a resistance wire having its ends fastened to said electrodes andits glow portion extending forwardly from the end of the plug, thefastening at least to the central electrode comprising a slightlytapered hole in the central electrode and a sleeve having one end ofsaid wire passing through the sleeve and fused thereto at its emergingend, the sleeve having a slight taper to grip the tapered hole in thecentral electrode when the sleeve is forced thereinto.

2. A glow plug including; a central electrode, a cooperative adjacentelectrode insulated from the central electrode, and a resistance wirehaving its ends fastened to said electrodes and its glow portionextending forwardly from the end of the plug, the fastening at least tothe central electrode comprising a slightly tapered hole in the centralelectrode and a sleeve having one end of said wire passing through thesleeve and fused thereto at its emerging end, the sleeve having a slighttaper to grip the tapered hole in the central electrode when the sleeveis forced thereinto,I the fastening to said cooperative electrode, whenspace will not permit a fastening as set forth for said centralelectrode, comprising a hole in said cooperative electrode to receiveone end of the resistance wire which is fused through the wall of thehole as by spot-welding, to its electrode.

3. A glow plug including; a central electrode,

a cooperative adjacent electrode insulated from the central electrode,and a resistance wire having its ends fastened to said electrodes andits glow portion comprising loop located in front of the end of theplug, the fastening including longitudinally arranged holes in the endsof both electrodes. at least the hole in the central electrode beingslightly tapered, and a sleeve over at least one end of the wire andfused thereto, the sleeve having a slight taper so when it is forcedinto the tapered hole in the central electrodes it will become securelyanchored thereto, the other end of the wire being located in the hole ofthe cooperative electrode and fused therein.

4. A glow plug as set forth in claim l, further defined in that at leastthe sleeve and at least that part of the electrode supporting it are ofmaterials having approximately the same temperature coefficient.

5. A glow plug including; a central electrode, a cooperative adjacentelectrode insulated from the central electrode. and a glow unitconsisting of a resistance wire having a glow portion and mounting ends,a sleeve on each of said ends and fused thereto, at least each. sleevebeing of a material having a temperature coefficient approximately likethat of the wire, the sleeves having a slight taper and the electrodeshaving holes in their ends of a slight taper to t that of the sleeve sothe sleeves are anchored securely to their respective electrodes whenforced into the holes in the electrodes.

6. A glow plug including; n. central electrode, a cooperative adjacentelectrode insulated from the central electrode, and a glow unitconsisting of a resistance wire having a glow portion and mounting ends,a sleeve on each of said ends and fused thereto and each having a slightoutside taper, the electrodes having slightly tapered holes in theirends to receive said sleeves which, after anchorage to the wire ends,are forced ini'o said holes so the tapered portions lock the partssecurely together.

1. A glow plug including; a central electrode, a cooperative adjacentelectrode insulated from the central electrode, and a glow unitconsisting of a resistance wire having a glow portion and mounting ends,means for anchoring the glow unit to the electrodes so the mountingrends of the wire are protected from the action of deleterious forceswithin the engine cylinder, said meansd comprising a sleeve over an endof the wire and fused thereto at the wire-emerging end, the sleevehaving a slight taper toward the wire end, while the electrode has aslightly tapered hole therein whereby when the sleeve is forcedthereinto it will be securely locked in place with the fused connectionbetween the wire end and sleeve adjacent the bottom of said hole.

8. A glow plug as set forth in claim '7, further defined in that thesleeve and at least the end of the electrode into which the sleeve isforced are of materials having approximately the same temperaturecoefficient.

9. Means for making connection between an end of a resistance unit and asupport member including a sleeve fused at its end to an end of theunit, the sleeve having a slight outside taper toward said fused end,the support member having a slightly tapered hole therein, whereby whenthe sleeve is forced thereinto it will be securely locked in place withthe fused connection between the wire end and sleeve adjacent the bottomof said hole.

10. An electrical joint in a heating plug for an internal combustionengine including, an element adapted to be heated by the passage ofelectric current therethrough, said element having a longitudinallyextending exterior surface and a sleeve attached thereto by a suitablefusion process, and an element having a hole therein and adapted to leadelectric current from an external source to the heater element, thejoint between said elements comprising said sleeve interposed inpress-fitting engagement with the wall of said hole in thesecond-mentioned element.

ADOLPH F. KLINGNER.

